The embodiments described herein relate to mechanisms for coupling firearm components, and more particularly to a rifle barrel nut for coupling a barrel and a handguard to a receiver of a firearm.
Known semi-automatic and automatic rifles operate under extreme conditions that can lead to significant wear in certain components, such as the rifle barrel. Additionally, it can be desirable to change the barrel configuration depending on the conditions under which the firearm will used. For example, shorter, lighter barrels are often used for close-quarters engagement, whereas longer, heavier barrels may be used in other situations (e.g., for improved accuracy when firing at greater distances). It can also be desirable to change the handguard, for example, to accommodate the user's preference for accessory mounting or for improved accuracy (e.g., by using a free-floating handguard). Accordingly, known semi-automatic and automatic rifles are configured to be repeatedly assembled and disassembled to accommodate changing the rifle barrel, the handguard, and other components.
Some known mechanisms for attachment of the rifle barrel and/or handguard, however, include a barrel nut that must be indexed with a gas port of the receiver or aligned with the gas tube that is coupled to the receiver. For example, some known barrel nuts used for an AR-15 rifle define a series of notches (or recesses) around the circumference of an outer flange. The notches are sized and/or shaped to receive a portion of the gas tube when the barrel is coupled to the receiver via the barrel nut. In certain instances, the notches can also be shaped to engage the mating lugs of a tool (or wrench) used to transfer torque to the nut during barrel installation. Thus, during the installation, such known barrel nuts are first tightened to a torque value within the specified torque range, for example 30 ft-lb (40.6 N-m). The wrench is then removed from the nut and the circumferential alignment is checked to verify whether one of the notches is aligned with the gas port. In fact, some known methods include using a separate alignment tool that simulates the positioning of the gas tube during rifle assembly to ensure proper alignment. If proper alignment is not achieved when the nut is initially tightened, the wrench is reapplied to the barrel nut, and the barrel nut is tightened incrementally until it is properly aligned.
Other known barrel nuts define a series of bores arranged circumferentially, and through which the gas tube passes. These barrel nuts nut must also be indexed (or circumferentially aligned) with the gas port of the receiver when the barrel is installed.
The iterative procedure used to align such known barrel nuts is time consuming and can result in misalignment that can negatively affect the performance of the rifle. Moreover, in certain instances, such known methods do not result in the desired alignment of the barrel nut within the torque specification. Specifically, in certain instances known barrel nuts can be tightened incrementally, as described above, up to the maximum torque value within the specified torque range (e.g., 80 ft-lb (108.3 N-m)), and still not be properly aligned. In such instances, additional assembly operations and parts, such as shims, may be needed to ensure proper alignment within the desired torque range of the nut.
Additionally, some known mechanisms for attachment of the rifle barrel and/or handguard include a barrel nut assembly that has multiple pieces. For example, some known barrel nut assemblies include a barrel nut and a spring-loaded delta ring. Such known designs are often referred to as “MIL-SPEC” designs, in reference to Military Specification MIL-C-71186 and other military specifications and standards that are related to the manufacture and assembly of these components. These known barrel nut assemblies allow for attachment of a two-piece (or split) handguard assembly. In addition to the issues identified with indexing (or circumferential alignment) discussed above, such known barrel nut assemblies also require that openings within the delta ring be aligned with the gas port. Moreover, methods of barrel and handguard assembly using such known assemblies include additional steps to assemble the barrel nut, delta ring, and spring.
Moreover, such known barrel nut assemblies do not accommodate mounting of a free-floating handguard. Similarly stated, such known barrel assemblies do not accommodate mounting a handguard only at the proximal (or receiver) end of the assembly, but rather require that the distal (or barrel) end of the handguard also be coupled to the rifle barrel.
In an effort to accommodate a free-floating handguard, some known barrel nuts include an outer diameter having mounting portions that receive a set screw or other fastener to secure the handguard thereto. Such known designs, however, require that the barrel nut be indexed (or circumferentially aligned) with the handguard to ensure that the handguard is properly aligned with the receiver, for example, to align the accessory rail portions of the receiver and handguard. Moreover, such known designs do not always ensure that the handguard is securely tightened against the receiver. For example, the use of some known barrel nuts can result in an undesirable gap between the receiver and the handguard (i.e., there is not a tight “lockup” between the receiver and the handguard).
Yet other known barrel nuts that accommodate a free-floating handguard require a series of steps to ensure proper axial alignment between a centerline of the barrel and a centerline of the handguard. For example, some known methods include sequentially and incrementally tightening the set screws when mounting the handguard to ensure that the handguard is axially aligned with the barrel.
Thus, a need exists for improved rifle barrel nuts for coupling a barrel and a handguard to a receiver without the need for time-consuming iterative alignment procedures, and that facilitates full engagement of the handguard to the receiver.